Cushioning means for steamactuated valves



ctc 8, iMGO L. B. JONES CUSHIONING MEANS FOR STEAM-ACTUATED VALVES 6Sheets-Sheet 1 Filed March 3, 1944 Nm a m wmm m a N. NN Q Q 5 1INVENTOR: llqydb. Jo/res,

ATTORNEYS.

6 Sheets-Sheet 2 Filed March 3, 1944 CUSHIONING MEANS FOR STEAM-ACTUATEDVALVES Oct 3, i946.

INVENTOR: Y 11050 5. Jones.

ATTORNEYS.

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I @Ci. 8, 5946. JONES CUSHIONING MEANS, FOR STEAM-ACTUATED VALVES 6Sheets-Sheet 4 Filed March 3, 1944 INVENTOR: a Zlaya B J01?es,

. ATTORNEYS;

Q Q %N Q w \& kgxiw @6250 194% L B, JONES CUSHIONING MEANS FORSTEAM-ACTUATED VALVES Filed March 5, 1944 6 Sheets-Sheet 5 x R. 5. m@ mHm W my w M A Z W @h 1946. B 2f33 CUSHIONING MEANS FOR STEAM-ACTUATEDVALVES Filed March 3, 1944 6 Sheets-Sheet 6 Patented Oct. 8, 19.46

UNITED sT -TEs PATENT" oFF cE s CUSHIONING MEANS FOR STEAM- ACTUATEDVALVES Lloyd B. Jones, Hollidaysburg"; Pa. Application March a, 1944,Serial No. 524,'s51

This invention has'general reference to fluidactuated reciprocatingengines and the means for controlling admission and exhaust ofmotivating medium to the cylinders'there'of. More particularly, theinstant improvements relate to a novel method and means for eilicientlycushioning the movements of the poppet-valves which control thedistribution of steam to the cylinder of locomotive engines.

Heretofore, and as well understood, thesteam distribution to modernlocomotive engine cylindders is generally controlled by admission andexhaust poppet-valves which, of necessity, must move with great rapidityand unless said valves be properly cushioned they are very liable todeteriorate or break, due to the heavy mechanical wear and tear imposedby normal service.

Bearing in mind the noted liabilities it is a primary object of theinstant improvements to positively overcome such liability byproviding'a novel method and means whereby the cushioning and quickaction of poppetevalves on locomotive engine cylinders is positivelyensured. In such connection two fundamental conditions are nec essarilyinvolved, namely thoseof proper cushioning,,and rapidity of motion.Accordingly another object of this invention is to provide novelimprovements, preferablyior incorporation in poppet-valves, whereby saidfundamental condi-' tions are positively interassociated or eflicientlycorrelated.

A further object is to provide .novel means effective to positivelycushion the terminal impact of a poppet-valve operating-piston at oneend of the stroke byfluid pressure inserted against an axially andspacially aligned relatively small coactive piston, and at the other endof thestroke by compression of presssure fluid in a special orcircumferential cavity surroundingly intermediate the end of saidpiston.

A. still further object is to insure promptresponsive actuation of apoppet-valve operatingpiston When thefluid pressure acting to cushionthe terminal portions of its stroke is released to.

exhaust.

Other objects with ancillary advantages will be duly noted or becomeapparent to those skilled in the art. upon a full understanding of theconstruction, arrangement and operation of the means hereinafterdisclosed.

,Forthe purpose. of illustrating this invention. there is shown by theaccompanying six sheets of drawings a typical embodiment of a, preferredmeans which has been found in practiceto definitely carry outthe'objects above statedi al- 7 Claims. (01. 121 132) 1 though it is tobe understood said means'is not conclusive, inasmuch as it may beotherwise 'arranged and organized with corresponding advantageousresults; hence the instant disclosure should not be considered aslimitative other'than reasonable interpretation of the concluding claimsrequires.

In the drawings:

Fig. 1 is a fragmentary sectional view of apart of an engine cylinderincluding admission poppet-' valve as well as the associated pilot, andflow connections, in accordance with the'instant invention, all of saidvalves being shown as in open position,

Fig. 2 is a similar sectional view-to the-prec'ed ing but illustratingthe respective valves differently located, or in the closed positionwith the pilot in proper position to keep said valves closed.

Fig. 3 is a larger scale sectional view of one of the admissionpoppet-valves shown in and 2, but illustrating said valve inanintermediate' location or as proximate to closed position.

Fig. 4 is a similar sectional view to Fig. 3 but showing the admissionpoppet-valve approaching the full open position. 1 I

Fig. 5 is a Sectional view similar to Fig.1 of the exhaust poppetandpilot-valves, as well as the associated flow connections, with all ofsaid valves in open position. v V v Fig. 6 is a corresponding sectionalview to Fig. 5, but showing the valves in closed position; Fig. 7 is asectional view, corresponding toFig. 3, of the exhaust poppet-valve,Fig. 8 is a s'imilar view to Fig. 4; of the exhaust poppet-valve.-

Fig. 9 is a fragmentary sectional detail view taken on the planedesignated by the angle-are Referring in greater detail to the drawingsand,

more particularly to Figs. 1, 2, 5 and 6, the ref-- erence character itdesignates a fragmentary portion of a locomotive engine" cylinder havinga cylinder port I2 under control of admission and exhaust poppet-valves[3, respectively; while l5 indicates the steam chest and IS the exhaustto the preceding" passage. The admission and exhaust poppetvalves l3, Mrespectively have companion pilotvalves l1, l8; said pilot-valves beingindividually shiftable by push-rods I9, 20 under actuation of a mastercontrolling cam, not shown; all of which parts are substantially inaccordance with my prior Patent No. 2,260,458, dated October 28, 1941.

In Fig. 1 two admission poppet-valves l3 with their controllingpilot-valve H, are shown'in' po sition in the steam chest I5, saidpilot-valve being equipped with a suitable rocker 2| whereby it isvertically activated from the associated pushrod IS, in a manner wellunderstood without .further elaboration herein. Note is to be had, at

this juncture, that the return movement of the.

pilot-valve I1 is accomplished by steam-chest pressure being directlyadmitted from the-latter through a port 22 into a chamber 23, undercontrol of a ball-valve 24, and being lifted from its lower seat 25,, asreadily understood from Fig. l. On the other hand, when the locomotivethrottle is. closed, and there is nopressure in the steamchest l5,steam, from another source of supply such as the drifting control means,is admitted below the pilot-valve IT by way of a manifold 26 andflow-passage 21 and aduct 28, in the steam-chest cover 29, with forcingof the ballvalve from its upper seat 30 onto the lower seat 25 andclosure of the port 22, whereby the pilotvalve I1 is maintained inproper position with respect to the push-rod l9.

As the several admission and exhaust poppetvalve l3, H are substantiallyalike and conformatory with known structure the following descriptionwill be confined to the changes therein made, in order to avoid thenecessity of needless descriptive matter. It is to be observed, however,that the double-seating member 3| of the poppet-valve |3, Fig. 2, isheld closed to the associated seats 32, 33 respectively, by pressurefrom the steam chest 1 5 entering the bore 34 of the pilot-valve |-1,through a port 35, with fiow'along a mcond' passage 38, into the axialbore 31 of the valve part 38, to exert its force on top of theoperating-piston 39: as clearly understandable from the associatedarrows shown in Fig. 2. Contrariwise, opening .or movement of the .valvemember-3| away from the seats 32, 33 for passage of pressure, from thesteam chest l5, intothecylinder port I2, is accomplished by exhaustingthe first mentioned passage 3.6, when steamchest pressure acts on thelower-or smaller portion 40, of the operating piston 33. Moreparticularly it will be observed that in Fig. 2 the poppet-valves I3 areshown in closed position and the pilot valve I] located to keep saidpoppetvalves closed. .However, it is noteworthy that the manifold 26leading .tothe drifting-valve, not shown, has a dual function dependingon whether the main throttle is opened and pressure being maintained inthe steam chest |5.: also that as long as there is pressure in the steamchest i5 the ball check-valve 24 would remain against its upper seat 30as indicated: by .a dot-and-dash circle in Fig. 2, due to such pressurewhile the passage .21 and manifold 25 serve as an exhaust from the bore.54- and ports 52, 53. When the main throttle is closed, however, andthere is no longer any pressure maintained in the steam chest I thedrifting-valve will turn live'steam from the boiler into the manifold 26and passage 2-1, which, acting through the bore 54 and ports 52, 53 willhold the admission valve 13 in open position: and under such conditionsthe ball check-valve 24 will drop and rest on its lower seat 25 closingthe inlet port 22 from the steam chest l5, and thereby holding thepilot-valve l1 up or collectively engaging the push-rod IS. AS theoperating-piston 39 moves upward it engages the stem 43 of a smallcushioning-piston 44, operative in the bore 45 of the cap member 46 ofthe valve l3; while a closure gland 41, is suitably clamped to saidmember. Now it will be readily apparent that, when the passage 36 isexhausted; the volume 01' pressure under the cushioning-piston 44discharges through an inclined radial duct or ducts 48, see Fig. 4 tobest advantage, provided for the purpose, into the annular clearance 49about the tapering central portion 50 of the cap member 46, and fromthence to exhaust by way of the bore 31 of the valve element 38, as alsoindicated by associated arrows in Fig. l; whereupon steam-chest pressureentering through a central port or small orifice 5| in the closure gland41 acts on the cushioning-piston 44 to drive it inward, relative to theoperating-piston 39; or in a direction opposite to that of saidoperating-piston. Now it will be further seen and readily understood, onexamination of Figs. 1 and 2, that when the operating-piston 39 engagesthe inner or lower end of the stem 43 of the cushioning-piston 44, thesteam thereabove will be compressed and forced outwards or back into thesteam chest I5 through the orifice 5| above referred to, with the resultthat the operating-piston 39 is retarded or slowed down by the very highcompression developed on top of the cushioning-piston 44, whereby saidoperating-piston will be broughtto the end of its upward stroke Withoutany excessive blow or jar;

' or, in other words, the upward movement of the operating-piston 39 iseffectively cushioned.

Whentheoperating-piston 39 is in the up" position of Fig. 1, see alsoFig. 4, the pressure force-between the two pistons 39 and 44 isconnected by way of radial ports 52,53, as well as the bore 54, of asecond valve element 55, to the flow-passage 21 and drifting-controlmanifold 26. as indicated by. the associated arrows in Fig. 1; whiletheoperating-piston 39 is held in the up" position by steam-chestpressure acting on, or in, the hollow 4| of its smaller and lowerportion 40, asaforesaid.

Closing of the admission poppet-valve I3 is effected .by admission o1steam, from the associated pilot-valve H, to the passage 36 through thebore 31 ofthe valve part 3.8 and, as the operating-piston. 39 movesdownward, some of said steam will b diverted, indifierential volume, byway of a duct 36. and port. 51, see the lefthand side of Figs. 3 and 4more particularly, into the space or circumferential cavity c about thelower or smaller portion 40 of the operatingpiston 39, for a purpose nowto be explained. Incidentally it is to be observed that the cavity 0 isdefined by the stepped bore of the poppetvalve structure, or by a linerinsert 1' fitted therein; as readily understandable by those conversantwithth art. As the operating-piston 39 moves downward the port 52 isfirst cut-off and then the port 51, after which the diverted steam, ofdifferential volume, is trapped and forced at high pressure through theport 53, which is purposely made small, or critical, to insure adequatedown" cushioning, for the piston 39, while at the same time permittingthe high-pressure or compressed steam in the circumferential cavity c toescape or exhaust after saidpiston reaches the limit of its downmovement. This trapping of. the high-pressure steam in the cavity indifferential volume, results in slowing the downward movement of theoperating piston 39with the poppet-valve 3| on the seats 32, 33at aspeed so greatly reduced .that

any blow or jar is eliminated. 'It is also to be particularly notedthat'by properly proportioning the size and location of the ports 52,'53 as well as theduct 56 and port 51, any desired degree of cushioningcan be effected, with optimum results obtainable when the piston 39descends at maximum speed, with quick closing of the poppet-valve 3|;and said piston being effectively slowed during the terminal portion ofits downward travel. On the other hand, if the degree of compression inthe circumferential cavity 0 is not enough, the piston 39 will beinsuificiently slowed down and the poppet-valve 3| will strike the seats32, 33 with a hard and objectionable blow; or, conversely, if there bean excess of compression in said cavity the piston 39 will bounce orrebound a short distance, thereby opening the poppet-valve 3| when itshould be closed. Accordingly it is again stressed that the size andlocation of the ports 52, 53, as well as the duct and port 51respectively, should be accurately determined and maintained.

The port 52, which it will be seen on xamination of the drawings, islarger than the port 53, has a further function to that above explained;in that, by promoting quick action of the operating-piston 39 it alsokeeps the diiierential volume of steam connected to the exhaustflowpassage 21, while said piston 39 is in the up position, and therebyeliminates any upward force opposing said piston due to pressure.

of the differential volume in the cavity 0. Also, when the piston 39starts downward, it is opposed only by steam-chest pressure actingagainst the lower or smaller portion 4|) of said piston, which isreadily overcome incidentalto the larger area of the upper end of suchpiston; as is quite obvious.

Referring now, more particularly, to the arrangement of parts forcushioning the movement of the exhaust poppet-valves M, as shown inFigs. 5 to inclusive, all parts similar to those previously described,in connection with the admission poppet-valve l3, will be designated bycorresponding reference characters with an added prime exponent in orderto obviate unnecessary repetitive explanation. Live steam from thelocomotive throttle and steam chest [5 flows, by way of a passage 58 anda conduit 68 to one side, the lower for example, of a double-seatingcheck-valve 59, to hold the ball 5! elevated against the upper seat 62,and from thence into the hollow 53 of the lower portion of thevertically-operative piston 64, in the exhaust pilot-valve l3. When thelocomotive is drifting, and the locomotive throttle closed the ball 5|in the check-valve 59, drops to its lower seat 65, while steam from thedrifting control-valve, not shown, flows through a second passage 66 andconduit 6"! into the upper part of the check-valve 59, as well as to theexhaust pilot-valve I8, and thereby holds the ball 6| to the seat 65. Anorifice 68 in the check-valve 59 aiiords flow communication from thepassage 58' into a conduit 69 connecting with the bore 54 v of therespective valve elements 55; while said conduit 59 has branches [0each, in turn, leading to a flow-constricting port H in the wall of thepoppet-valve cylinder 12, whereby live steam from the throttle and steamchest I5 is afforded "access to' an auxiliary-cushioning'valve I3, lateron more fully explained.

In th position shown by Fig. 5 each exhaust poppet-valve I4 is open,with the associated operating-piston 39' at the top of its stroke. Thesmall cushioning-piston Mi, which conangled-duct M on the'downwardlyforced steam is sufficient to build-up a high degree of compressionagainst the cushioning piston 44 which materially slows down itsmovement. Now, it will be apparent that, with the operating piston 33 inthe position just described and inclined port '15, through the top ofthe poppet-valve structure that communicates from above theauxiliary-cushioning .valve 73 to the 'bore .31 of the exhaust-valvepart 38, is open to exhaust.

. A duct 16, from the lower end of the bore 11, in

movement,

which said valve 13 operates, is open to exhaust, as indicated by theassociated arrows in the lefthand side of Fig. 8, but it is to beremarked the valve 13 is held in its up position until it is blanked-offby upward movement of the piston 39. In other words live steam from theport H holds the auxiliary-cushioning'valve 13 in the "up position untilit is driven down by admission of steam on top of the piston 39, whichalso enters through the port 15;.while a port 19, indicated by dottedlines in Figs. 7 and 8 and shown in full in Figs. 9 and 10, is open toexhaust and thereby affords outlet for the steam in the circumferentialcavity 0 intermediate the upper and'lower portions of the operatingpiston 39 Turning now more particularly to Fig,'5,- when livegsteam isadmitted from the pilot-valve is through the conduit 80 to the top ofthe'operating-piston 39', the double-seating member 3| of thepoppet-valve M commences its downward live steam being also admittedthrough the inclined-port to the top of the auxiliary-cushioning valvel3, thereby moving the latter down and onto a seat 8|, just below thesteam flow-constricting port H, and thus closing the duct 18. With theauxiliary-cushioning valve 13 in the down position, just referred to,'aport 82 from the circumferential cavity 0 is opened to exhaust about thereduced part'83 of said valve I3 with outlet through an orifice 84 inthe'wall of the poppet-valve It, as readily seen onexamination of theleft-hand portion of Fig. 7, more particularly. As soon as theoperating-piston 39' starts down, the port 19 is closed by the smallerportion 49" of said piston, but the circumferential cavity 0 abovereferred to, still continues open to exhaustby way of the port 82 untilthe lower packing ring '85 about the upper portion of theoperating-piston 39' passes over said port. With the port 82 closed theremaining steam in the circumferential cavity 0 is compressed, as thedownward movement of the operating piston 39" advances and, as suchmovement continues, a lower or supply port 86, for live steam, isopened, whereby, there results a combination of compressed andentering'live steam pressures which, jointly'function to slow down thetravel of the operatingpiston 39' just before the poppet double-seatingmember 3| contacts theassociated seats 323 33,

and thereby efie'ctively cushions the impact of contact. Now it will beseen that, upon completion of the downward stroke of the operatingpiston39', the inner or lower end 81 of the duct 16 will be cut-off fromconnection to exhaust, whereas the upper end 88 of said duct is incommunication with the circumferential cavity c by way of the port 19,as before noted, and thus pressure steam is conducted to the lower orsmaller end of the auxiliary-cushioning valve 13, in. a, manner clearlyapparent upon examination of Fig. 6 of the drawings. At the same timelive steamis also admitted by way of the angled-duct 14 to the top ofthe cushioning piston 44', which is consequently moved inward to thelimit ofits downward stroke, incidental to the provision of an exhaustoutlet or port 89.

When the pilot-valve l8 again lifts or opens, the steam actin on thelarger or upper end of the operating piston 39' flows out or exhausts byway of the bore 31' of valve. element 38' and conduit 80, while the livesteam now filling the circumferential cavity 0, hereinbefore explained,causes said piston 39' to move upward, and thereby opens the poppet orlifts the double-seating member 3| from the seats 32', 33'. The actionjust described also effects exhaust of the pressure acting on top of theauxiliary-cushioning valve 13, by way of the inclined port 15, andpermits it to ascend by reason of the pressure steam acting thereunderthrough the duct 16. Such action, in turn, admits live steam to thesmaller reduced portion 90, of the auxiliary-cushioning valve 13, by wayof the duct 18 and causes said valve to lift and cut-oil or close theport 15 to exhaust, so that the circumferential cavity C is firstsupplied with live steam through the port 86and later by way of the duct18, until said piston reaches the limit of its up-stroke, by which timethe duct 18 is cut-off incidental to passage thereover of the upper ring92 of the smaller portion 40' of the piston 38, as clearly seen onreference to Fig. of the drawings; while the. port 19 is now open toexhaust as hereinbefore stated. The port 19 is also blanked or shut-offfrom the. circumferential cavity 0, as the piston 39 moves upward, andopens to exhaust, as before described, to thereby exhaust the steam frombelow the lower end of the auxiliary-cushioning valve 13. Toward the endof the up-stroke of the operating piston 39', it engages the confrontingend of the stem portion 43' of the cushioning-piston 44 and is therebyslowed down during the end portion of its stroke, as explained inconnection with the admission poppet-valves l3 of Figs. 1 to 4,inclusive.

From the foregoing it will be seen that the movement of the operatingpiston 39' is efi'ectively cushioned as it approaches the limit of itsstroke, in one direction, by means of the piston 44, and. at the otherend of its stroke by the compression of steam in the circumferentialcavity 0, supplemented by admission of live steam through the port 86,which latter condition also insures the prompt response of the piston39' to upward movement when the steam on top of it is exhausted by thepilot-valve 18; while any steam about the upper part of said pilot-valveflows to exhaust [6 by conduits 9|, in an obvious manner. It is also tobe particularly remarked that by the arrangement of the several portsand ducts, as above described, said arrangement and careful dimensioningthereof, serve to materially speedup the movement of theoperating-piston 39 or 39', as well as insuring and promoting quickopening and closing of the respective poppetvalves 3| or 3i. With the.piston 3.9 at the top of its stroke, the port 19 exhausts thecircumferential cavity c, so that the larger portion of said piston canrespond quickly when steam is admitted on top of it and, since the port82 remains open to exhaust 'until the piston 39' has nearly completedits down stroke, there is but little. resistance to such down movementuntil it isessential to slow it up toward the end of the stroke.Similarly, the port 18 continues to supply live steam to thecircumferential cavity 0, during the up stroke of the piston 39', untilit is cut-off by the upper piston ring 92, Figs. '1 and 8, just beforethe port 19 opens to exhaust at the terminal part of said stroke.Effective cushioning of the exhaust poppet-valves I4 is thereforeaccomplished with a minimum of moving parts, while such parts as arerequisite, simply consist of the cushioning-piston 44 or M", and theauxiliary-cushioning valve 13; all of which valves are comparativelysmall, have limited movement and, consequently, are subject to minimumwear.

From the foregoing it is considered the merits and advantages of thepoppet-valve cushioning means hereinbefore disclosed will be clearlyapparent; also that the explained embodiment thereof fully justifies theobjects set forth in the prefatory paragraphs of this specification; andfurthermore that changes may be made in the form, location, and assemblyof the various parts, without departing from the spirit of saidinvention as comprehended within the scope of the following claims.

Having thus described my invention, I claim:

1. In a locomotive engine having piston-operated poppet-valvescontrolling the admission and exhaust of pressure-steam to the enginesteam chest and cylinder, with individual pilotvalves effective to openand close said poppetvalves, means for cushioning the terminal impactsof the operating-piston, said means comprising a relatively smallindividually and axiallyshiftable piston, said piston beingspacedlyaligned in respect to the poppet-valve operating piston at oneend thereof; means in the body of the poppet-valve defining acircumferential cavity about and intermediate the ends of the operatingpiston; and conduit means with asso ciated ports controlling supply ofpressure from the cylinder steam chest to and from the smallaxially-shiitable piston, as well as to the circumferential cavity foreffecting positive cushioning of the poppet-valve operating-piston whenapproaching the limits of its movement.

2. The combination of claim 1 wherein a small port or orifice isprovided in the poppet-valve axially outward relative to the smallshiftablepiston for the admission of steam-chest pressure to drive saidpiston in one direction, and means forming a part of the shiftablepiston for engagement by the poppet-valve operating piston to effectexpulsion of the admitted steam-chest pressur above the shiftable-pistonunder high compression whereby the poppet-valve operatingpiston iseffectively cushioned.

3'. The combination of claim 1 wherein one of the supply ports is of acritical size to restrict exhaust of steam compressed in thecircumferential cavity, and one of the conduit means with an associatedport serves to divert steam-chest pressure directly into said cavity topositively insure adequate cushioning of the poppet-valveopcrating-piston during the terminal parts of its strokes and therebyprevent the valve from striking its seat.

4. The combination of claim 1 wherein a double-seating ball-valve isprovided in connection with the pilot-valve controlling the steamadmission poppet-valve, and an associated conduit and port meanssupplies pressure-steam to said ballvalve, from another source than thesteam chest, to shut-off the pilot-valve from actuation, by steam-chestpressure, when the locomotive is drifting.

5. The combination of claim 1 wherein the operating-piston of thepoppet-valves embodies hollow-sections of different diameter, and thecircumferential cavity in the poppet-valve body is defined by anassociated insert within the body of the poppet-valve.

6. In a. locomotive engine having piston-operated poppet-valvescontrolling the admission and exhaust of pressure-steam to the steamchest and cylinder thereof, with individual pilot-valves effective toopen and close said poppet-valves; means operative to effect cushioningof the terminal impacts of the operating-piston, said means comprising arelatively small axially-related shiftable-piston having a stem with itsinner end normally spaced away from the confronting end of saidoperating-piston; means in the body of each poppet-valve defining anannular cavity, about and intermediate the ends of the operatingpiston;an auxiliary cushioning-valve in the aforesaid poppet-valve bodycooperative with the axially shiftable-piston; and means in the form ofducts and ports efiective to supply live steam to as well as steam underconstricted flow through said auxiliary cushioning-valve, whereby theterminal portions of the stroke of the operatingpiston in eitherdirection are efiectively slowed down and noisome impacts positivelyprevented.

7. The combination of claim 6 wherein the axially shiftable-piston has astem adapted for coaction with the confronting end of the poppetvalveoperating-piston, conduit means from the pilot-valve, with associatedports for supplying live steam from the pilot-valve tomove thepoppet-valve Operating-piston in one direction, and to divert a part ofsuch supply for concurrent movement of the auxiliary shiftable-piston inthe same direction to open a port in the valve toexhaust, individualports in the body of the valve for maintenance of the circumferentialcavity open to exhaust until the operating-piston approaches the end ofits stroke in the direction. aforesaid, and other conduit means withassociated ports admit live steam to the circumferential cavity and tothe auxiliary shiftable-piston for movement of the latter in the reversedirection and to adequately cushion the first mentioned relatively smallshiftable-piston.

LLOYD B. JONES.

